/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.coders;



import com.bff.gaia.unified.sdk.util.ExposedByteArrayOutputStream;

import com.bff.gaia.unified.sdk.util.StreamUtils;

import com.bff.gaia.unified.sdk.util.VarInt;

import com.bff.gaia.unified.sdk.values.TypeDescriptor;

import com.bff.gaia.unified.vendor.guava.com.google.common.base.Utf8;

import com.bff.gaia.unified.vendor.guava.com.google.common.io.ByteStreams;



import java.io.*;

import java.nio.charset.StandardCharsets;



/**

 * A {@link Coder} that encodes {@link String Strings} in UTF-8 encoding. If in a nested context,

 * prefixes the string with an integer length field, encoded via a {@link VarIntCoder}.

 */

public class StringUtf8Coder extends AtomicCoder<String> {



  public static StringUtf8Coder of() {

    return INSTANCE;

  }



  /////////////////////////////////////////////////////////////////////////////



  private static final StringUtf8Coder INSTANCE = new StringUtf8Coder();

  private static final TypeDescriptor<String> TYPE_DESCRIPTOR = new TypeDescriptor<String>() {};



  private static void writeString(String value, OutputStream dos) throws IOException {

    byte[] bytes = value.getBytes(StandardCharsets.UTF_8);

    VarInt.encode(bytes.length, dos);

    dos.write(bytes);

  }



  private static String readString(InputStream dis) throws IOException {

    int len = VarInt.decodeInt(dis);

    if (len < 0) {

      throw new CoderException("Invalid encoded string length: " + len);

    }

    byte[] bytes = new byte[len];

    ByteStreams.readFully(dis, bytes);

    return new String(bytes, StandardCharsets.UTF_8);

  }



  private StringUtf8Coder() {}



  @Override

  public void encode(String value, OutputStream outStream) throws IOException {

    encode(value, outStream, Context.NESTED);

  }



  @Override

  public void encode(String value, OutputStream outStream, Context context) throws IOException {

    if (value == null) {

      throw new CoderException("cannot encode a null String");

    }

    if (context.isWholeStream) {

      byte[] bytes = value.getBytes(StandardCharsets.UTF_8);

      if (outStream instanceof ExposedByteArrayOutputStream) {

        ((ExposedByteArrayOutputStream) outStream).writeAndOwn(bytes);

      } else {

        outStream.write(bytes);

      }

    } else {

      writeString(value, outStream);

    }

  }



  @Override

  public String decode(InputStream inStream) throws IOException {

    return decode(inStream, Context.NESTED);

  }



  @Override

  public String decode(InputStream inStream, Context context) throws IOException {

    if (context.isWholeStream) {

      byte[] bytes = StreamUtils.getBytesWithoutClosing(inStream);

      return new String(bytes, StandardCharsets.UTF_8);

    } else {

      try {

        return readString(inStream);

      } catch (EOFException | UTFDataFormatException exn) {

        // These exceptions correspond to decoding problems, so change

        // what kind of exception they're branded as.

        throw new CoderException(exn);

      }

    }

  }



  @Override

  public void verifyDeterministic() {}



  /**

   * {@inheritDoc}

   *

   * @return {@code true}. This coder is injective.

   */

  @Override

  public boolean consistentWithEquals() {

    return true;

  }



  @Override

  public TypeDescriptor<String> getEncodedTypeDescriptor() {

    return TYPE_DESCRIPTOR;

  }



  /**

   * {@inheritDoc}

   *

   * @return the byte size of the UTF-8 encoding of the a string or, in a nested context, the byte

   *     size of the encoding plus the encoded length prefix.

   */

  @Override

  public long getEncodedElementByteSize(String value) throws Exception {

    if (value == null) {

      throw new CoderException("cannot encode a null String");

    }

    int size = Utf8.encodedLength(value);

    return (long) VarInt.getLength(size) + size;

  }

}